328: Add reference implementation

bip-0328/_base58.py

@@ -0,0 +1,176 @@
+"""
+Base 58 conversion utilities
+****************************
+"""
+
+#
+# base58.py
+# Original source: git://github.com/joric/brutus.git
+# which was forked from git://github.com/samrushing/caesure.git
+#
+# Distributed under the MIT/X11 software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#
+
+from binascii import hexlify, unhexlify
+from typing import List
+
+from _common import hash256
+
+
+b58_digits: str = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
+
+
+def encode(b: bytes) -> str:
+    """
+    Encode bytes to a base58-encoded string
+
+    :param b: Bytes to encode
+    :return: Base58 encoded string of ``b``
+    """
+
+    # Convert big-endian bytes to integer
+    n: int = int('0x0' + hexlify(b).decode('utf8'), 16)
+
+    # Divide that integer into base58
+    temp: List[str] = []
+    while n > 0:
+        n, r = divmod(n, 58)
+        temp.append(b58_digits[r])
+    res: str = ''.join(temp[::-1])
+
+    # Encode leading zeros as base58 zeros
+    czero: int = 0
+    pad: int = 0
+    for c in b:
+        if c == czero:
+            pad += 1
+        else:
+            break
+    return b58_digits[0] * pad + res
+
+def decode(s: str) -> bytes:
+    """
+    Decode a base58-encoding string, returning bytes
+
+    :param s: Base48 string to decode
+    :return: Bytes encoded by ``s``
+    """
+    if not s:
+        return b''
+
+    # Convert the string to an integer
+    n: int = 0
+    for c in s:
+        n *= 58
+        if c not in b58_digits:
+            raise Exception('Character %r is not a valid base58 character' % c)
+        digit = b58_digits.index(c)
+        n += digit
+
+    # Convert the integer to bytes
+    h: str = '%x' % n
+    if len(h) % 2:
+        h = '0' + h
+    res = unhexlify(h.encode('utf8'))
+
+    # Add padding back.
+    pad = 0
+    for c in s[:-1]:
+        if c == b58_digits[0]:
+            pad += 1
+        else:
+            break
+    return b'\x00' * pad + res
+
+def decode_check(s: str) -> bytes:
+    """
+    Decode a Base58Check encoded string, returning bytes
+
+    :param s: Base58 string to decode
+    :return: Bytes encoded by ``s``
+    """
+    data = decode(s)
+    payload = data[:-4]
+    checksum = data[-4:]
+    calc_checksum = hash256(payload)
+    if checksum != calc_checksum[:4]:
+        raise ValueError("Invalid checksum")
+    return payload
+
+def encode_check(b: bytes) -> str:
+    checksum = hash256(b)[0:4]
+    data = b + checksum
+    return encode(data)
+
+def get_xpub_fingerprint(s: str) -> bytes:
+    """
+    Get the parent fingerprint from an extended public key
+
+    :param s: The extended pubkey
+    :return: The parent fingerprint bytes
+    """
+    data = decode(s)
+    fingerprint = data[5:9]
+    return fingerprint
+
+def get_xpub_fingerprint_hex(xpub: str) -> str:
+    """
+    Get the parent fingerprint as a hex string from an extended public key
+
+    :param s: The extended pubkey
+    :return: The parent fingerprint as a hex string
+    """
+    data = decode(xpub)
+    fingerprint = data[5:9]
+    return hexlify(fingerprint).decode()
+
+def to_address(b: bytes, version: bytes) -> str:
+    """
+    Base58 Check Encode the data with the version number.
+    Used to encode legacy style addresses.
+
+    :param b: The data to encode
+    :param version: The version number to encode with
+    :return: The Base58 Check Encoded string
+    """
+    data = version + b
+    checksum = hash256(data)[0:4]
+    data += checksum
+    return encode(data)
+
+def xpub_to_pub_hex(xpub: str) -> str:
+    """
+    Get the public key as a string from the extended public key.
+
+    :param xpub: The extended pubkey
+    :return: The pubkey hex string
+    """
+    data = decode(xpub)
+    pubkey = data[-37:-4]
+    return hexlify(pubkey).decode()
+
+
+def xpub_to_xonly_pub_hex(xpub: str) -> str:
+    """
+    Get the public key as a string from the extended public key.
+
+    :param xpub: The extended pubkey
+    :return: The pubkey hex string
+    """
+    data = decode(xpub)
+    pubkey = data[-36:-4]
+    return hexlify(pubkey).decode()
+
+
+def xpub_main_2_test(xpub: str) -> str:
+    """
+    Convert an extended pubkey from mainnet version to testnet version.
+
+    :param xpub: The extended pubkey
+    :return: The extended pubkey re-encoded using testnet version bytes
+    """
+    data = decode(xpub)
+    test_data = b'\x04\x35\x87\xCF' + data[4:-4]
+    checksum = hash256(test_data)[0:4]
+    return encode(test_data + checksum)